Even 150 years later, no one can say for sure what started the bloody feud between the Hatfields of West Virginia and the McCoys of Kentucky.

Some think it was shifting allegiances during the Civil War that drove a wedge between the two neighboring families. Others point to a pull-and-tug over land, timber and money. And some feel it was a prized pig, lost or waylaid, that sent the mountain clans into decades of murders and vengeance.

Bits of all those theories, plus a disastrous Romeo-and-Juliet love story, lay the foundation for History channel's "Hatfields & McCoys," a six-hour miniseries launching Monday.

"We wanted to show how a series of incidents swept everybody up in this tornado of ego, jealousy, bitterness and violence," said Leslie Greif, one of the project's executive producers, who's been working to get the story to screen for nearly 20 years. "Never forgiving, never forgetting took over, and pretty soon they were in the middle of a war and didn't even know how they got there."

The three-night event stars western-movie veteran Kevin Costner, who Greif called "the Gary Cooper of our day." Costner plays Devil Anse Hatfield, a war deserter, entrepreneur and, at times, cold-blooded killer. Also top billed are Bill Paxton as Randall McCoy, patriarch of the McCoy clan, an unrecognizable Tom Berenger as the sociopathic "Uncle Jim" Vance, Powers Booth, Mare Winningham and Jena Malone. The show chronicles about 30 years, a dozen brutal killings and innumerable heartaches in the lives of the two populous families.

Despite its iconic status, there have been few dramatic depictions of the inter-family battle either on TV or in film. It's been portrayed most often as comic or cartoonish — or both, in the case ofWarner Bros.' famous Bugs Bunny musical short, "Hillbilly Hare" — making it ripe for serious treatment, said Nancy Dubuc, president and general manager of History and an executive producer on the miniseries.

"It's a big pre-sold headline that everybody knows but nobody knows," Dubuc said. "It's part of American pop culture, but very few people could tell you the true story of these families."

Costner, whose involvement as a star and producer lighted a fire under the project, said he was attracted to the complexity of the story. As an American-history buff, he had "a working knowledge" of the Hatfields and McCoys and said he welcomed the chance to dig deeper.

"I tried to be an emotional detective," Costner said. "While I thought about the political and economic forces at play — plus the potent combination of alcohol, guns and misery — I wanted to find the humanity in these tough, hardened people."

The Oscar-winning actor-director was so moved by the story that he and his roots-rock band, Modern West, recorded a concept album based on the miniseries, titled, "Famous For Killing Each Other." The music will be used in the movie and a companion making-of documentary.

Though not actually filmed in Appalachia — the incentives are better in Romania, producers said — the miniseries tries to capture accurately details of the family fight that eventually involved theU.S. Supreme Court, made international headlines and nearly pushed Kentucky and West Virginia to the brink of war.

Historians and educators vetted the story, Greif said, though producers took some dramatic license to allow for composite characters and dialogue. Among its tragic turning points are the execution-style murders of three of McCoy's sons, theNew Year's Dayfirebombing of their home and the public hanging of a mentally disabled member of the Hatfield clan.

This is History's second attempt, but first actual airing of a scripted miniseries. The network aborted plans to run its initial project, a controversial 2011 version of "The Kennedys," which landed on ReelzChannel and later won four Emmy awards.

History started developing miniseries as a natural evolution in its programming, Dubuc said, and "Hatfields & McCoys" provided the fodder to "make some noise" with its male-skewing audience. Viewers had already responded to Hatfield and McCoy lore, included in anthologies and documentaries that have aired on the channel over the years.

To bolster the miniseries, which will unfold over three consecutive nights, History has planned a number of programming stunts around it. The channel will air a two-hour documentary, "America's Feud: Hatfields & McCoys," and themed episodes of its top series, "Pawn Stars" and "American Pickers."

Eye-catching marketing, including subway wraps in New York, trailers in movie theaters and sponsorship of HBO's recentFloyd Mayweather Jr.-Miguel Cotto pay-per-view boxing match, has surrounded the project as well.

At its core, "Hatfields & McCoys" deals with themes that run through centuries of literature, said Leo Braudy, USC professor of mass media and pop culture.

"It touches on old-time vendettas, people with a past, enmities that go back decades," he said. "It's classic conflict of the most intimate kind, and that always has the potential to be compelling."